REGARD 8-Input 4-20 Module & 8-Channel Display Card (ATEX Version)
Issue 2. October 2011
6
OPERATION
Intended use
The
REGARD
8-channel display card and 8-input 4-20 module provide:
•
Measurement and display of gas level with gas measuring heads (transmitters) such
as Polytron 2. The equipment can be used with any 4-20mA transmitter.
•
Activation of alarms when pre-set gas levels are exceeded.
The input module and display card are intended for permanent installation in a non-
hazardous environment, such as a control room or marshalling cabinet.
Description
Genera
l
The 8-input 4-20 module takes signals from up to eight 2-wire or 3-wire 4-20mA
measuring heads (transmitters). The module provides terminals for field cables and DC
power to the transmitters. Signals from the eight inputs are multiplexed onto an RS-485
connection for transmission to the 8-channel display card. The display card displays the
gas level of each head and indicates alarm and fault conditions.
The display card has three alarm relays for
•
A1 gas alarm
•
A2 gas alarm
•
Fault
alarm
Each 8-input module requires an 8-channel display card. Only one module can be
connected to a display card.
The input module and display card can be located in separate enclosures or buildings.
The maximum distance of the RS-485 cable between the module and display card is
1km.
Power-on sequence
When power is applied to the display card, it is immediately inhibited and put into its
default state, all relays are de-energised. After about two seconds, when the
configuration settings have been read from the non-volatile memory, these settings are
applied. So if the A1 and A2 relays are set normally energised, they will change state.
The display card remains inhibited for a user definable period (default is the minimum of
30 seconds) allowing time for heads connected to the input module to settle. During this
period no data from the input module is processed by the display card. Once this power-
on inhibit period has elapsed data begins to be read from the module and the display
card enters its normal operating state.
